The present invention relates to a process and apparatus to attach elastic members to a disposable wearing article being continuously manufactured such as a disposable diaper or training pants. The present application is based on, and claims priority from, Japanese Application Serial Number 2002-328829, filed Nov. 12, 2002, the disclosure of which is hereby incorporated by reference herein in its entirety.
In the course of continuously manufacturing disposable wearing articles such as disposable diapers, it is well known to feed continuous elastic members toward a single continuous web being fed in a machine direction as a component member of the article while these continuous elastic members are oscillated in a cross direction relative to the machine direction and to attach these continuous elastic members in a stretched state to the continuous web. For example, in the case of the process and the apparatus for attachment of the elastic members to the pull-on diaper disclosed in Japanese Patent Application Publication No. 1999-332913A, guide means for positioning of the elastic members are provided so as to be opposed to the web continuously fed in the machine direction. These guide means are oscillated in the cross direction orthogonal to the machine direction by driving means including a servo mechanism.
The servo mechanism adopted by the apparatus disclosed in the above cited publication comprises a servomotor and a timing belt connecting an output shaft of the servomotor with the positioning guide means so that the positioning guide means may move along a rectilinearly extending feed means as the timing belt travels. In this well-known apparatus, a rotational velocity of the servomotor depends on various factors such as an inertia of the timing pulley mounted on the output shaft of the servomotor and rotating together with the output shaft, an inertia of the traveling belt, an inertia of the positioning guide means moving along the feed means, a vibration of the belt during its traveling and a friction between the positioning guide means and the feed means. These factors interfere with rotation of the servomotor at a high speed and consequently impede a production rate for the diaper from being improved.